Cystathionine γ-synthase: Studies on the γ replacement reaction
1972; Elsevier BV; Volume: 276; Issue: 1 Linguagem: Inglês
10.1016/0005-2744(72)90030-7
ISSN1878-1454
Autores Tópico(s)Cancer Research and Treatments
ResumoCystathionine γ-synthase from Salmonella catalyzes the γ replacement reaction in which O-succinyl-l-homoserine and l-cysteine form succinic acid and cystathionine, an important intermediate in methionine biosynthesis. In the absence of l-cysteine the enzyme catalyzes a γ elimination reaction in which O-succinylhomoserine is decomposed to α-ketobutyrate, NH3 and succinic acid. β-Mercaptopropionic acid, a non-competitive inhibitor of γ elimination, has been shown to be a substrate for the γ replacement reaction. The reaction product has been identified, by mass spectroscopy, as S-carboxyethyl-l-homocysteine. A kinetic study of this γ replacement reaction has demonstrated that β-mercaptopropionic acid has no effect on the enzyme's affinity for O-succinylhomoserine. It is suggested that the γ replacement reaction with l-cysteine is kinetically similar to that with β-mercaptopropionic acid.
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